Heavy metals form a significant part of environmental pollution. They occur in water and in the soil in the form of their dissolved or relatively easily soluble compounds. Mercury, arsenic, lead, cadmium, copper, zinc, etc. are toxic and must therefore be removed from the water cycle and the soil. | Theoretically, there are several ways to separate heavy metals from wastewater. These are e.g. precipitation, ion exchange, electrolysis or ultrafiltration.